EGR valves under the spotlight

Chief among NTK´s components is the exhaust gas recirculation (EGR) valve, a central element in a vehicle’s emissions system, whose core role is to reduce an engine’s combustion peak temperature and thus hinder the formation of dangerous nitrogen oxide (NOx) gases. This part achieves this vital action by transferring combustion gases from the exhaust manifold into the intake manifold and back into the engine cylinders. In this way, the oxygen in the incoming air stream is diluted, which creates inert gases that help to absorb some of the heat generated by the combustion process. This, in turn, reduces peak cylinder temperatures and therefore hinders the formation of NOx. This type of pollution can be particularly irritating to the human respiratory system and can lead to lung damage. In addition to its effect on human health, it also contributes to ozone pollution at ground level, which is harmful to trees and other plant life.  

Different types of EGR valves

Currently, all new diesel cars have EGR valves fitted, with around a third of modern petrol vehicles using the component. In the case of diesel models, some even have two valves, one a low-pressure unit and one a high-pressure item. The two diesel EGR valves have different roles: the high-pressure part takes high flowing sooty exhaust gases and diverts them before they enter the diesel particulate filter (DPF), feeding them back into the inlet manifold. Low-pressure valves deal with slower, cooler gases that have been stripped of their sooty deposits in the DPF. These are then also passed back into the inlet manifold.

Essentially there are three overall types of EGR that NTK Vehicle Electronics offers: the pneumatic, electric and electric variant with integrated cooler. The first of these is distinct in having a vacuum-controlled diaphragm, while the electric variant is controlled through electronics that can be regulated in absolute precision by the engine control unit (ECU). The addition of a cooling unit helps to further reduce the temperature of the exhaust gases. In diesel engines, the EGR is controlled by Mass Air Flow (MAF) sensors, which assesses the amount of intake air that the engine takes in to combine with the fuel and passes information on the mass flow of air to the ECU, which then uses this data to calculate the correct quantity of petrol needed by the engine. The EGR is usually positioned either on the side of, or on top of the engine, close to the intake manifold. It is connected with a tube to the exhaust.

The market coverage of the EGR valve

In January 2022, NTK Vehicle Electronics increased its already extensive range of Aftermarket sensors to include EGR valves. Currently there are 185 part numbers in the line-up, which represents an EMEA car parc coverage of 127 million vehicles in operation (VIO), equating to 51% coverage of all diesel and petrol applications that are equipped with an EGR valve. This extensive reach is reflective of the NTK brand’s valued reputation in offering reliable, hard-wearing components that are backed by decades of exhaustive R&D and extensive testing.

As a result, the EGR, like all Aftermarket Niterra parts, is engineered to match OE standards in performance and reliability and customers can rest assured that it has undergone a process of evaluation that includes thermal shock testing under temperatures ranging from -40°C to 150°C, together with tests on valve, cavity and cooling leakage, its electrical resistance, and its anticipated lifecycle.

Possible problems with the EGR valve

As with any high-tech component, problems can occur and careful maintenance is recommended. In the event of engine issues, drivers will first be alerted to a problem with their EGR through an engine warning light on the dashboard. If this happens, they are advised to check the manufacturer’s instructions before either repairing or replacing a valve. As with many parts housed within a combustion engine, the EGR’s performance can be impaired by a buildup of soot, oil or oil vapour entering the combustion chamber, as well as an incorrect mixture of air and fuel. Other factors that can impede an EGR valve’s correct functioning can include defective glow plugs (in the case of a diesel engine) or using a diesel vehicle extensively for short journeys that do not allow the regeneration of the DPF.

Typically, these problems lead to an engine idling poorly or jerking and knocking whilst driving. Substandard performance and fuel economy will be observed and, in extreme cases, the vehicle will fail to start. It is always advisable to address any problem with an EGR valve promptly, as failure to do so can lead, in a worst-case scenario, to expensive repairs or the necessary replacement of the vehicle’s DPR filter or turbocharger.

Conclusion

This feature is part of a series of articles that aim to give the reader some basic information and background on the technical aspects of the product ranges offered by Niterra’s NGK Ignition Parts and NTK Vehicle Electronics brands. The next subject under the spotlight will be the exhaust gas & differential pressure sensors, another important element in the engine’s combustion process and a key component in ensuring powertrains run efficiently and cleanly.
 

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